The invention relates generally to dental appliances and synthetic compositions used to make them. More particularly, the invention concerns an improved interocclusal appliance which provides improved appliance retention and precise vertical and lateral positioning of the mandible, as well as a method of forming such appliance, and a curable composition for making dental appliances such as the invented appliance.
Interocclusal appliances, commonly referred to as splints, are well known, and are used to secure or hold in proper position (or desired range of positions) the mandible of a patient. Splints may be used for orthodontic treatment, as well as for orthopedic treatment of the bone, joints and supporting tissue associated with the mouth.
For example, splints are used to treat various conditions including temporomandibular joint (TMJ) dysfunction syndromes, myofascial pain dysfunction syndrome, and symptomatic or asymptomatic loss of tooth structure from subconscious parafunctional mandibular habits known as bruxism (grinding) or clenching. Splints are also used to reduce wear on teeth caused by metal or porcelain dental restorations during normal, functional or parafunctional mandibular movement. Splints may also be used as anti-snoring devices to resolve snoring problems and obstructive sleep apnea (OSA).
Several unimaterial, conventional splints have been proposed but there are certain problems common to all of them. First, none of the so-called "soft" splints remain soft over time. Conventional splints harden over time due to their composition and/or due to leaching out of unreacted plasticizers present in them. Such hardening is a drawback because soft, resilient splints are preferred. Soft splints are preferred because they are more comfortable to wear than hard appliances, and because they provide improved retention of the splint held by the teeth.
A second drawback associated with such splints is that they are notoriously imprecise in terms of vertical and lateral positioning of the mandible under desired patient-bite conditions before they harden. Precise vertical and lateral positioning of the mandible is critical to proper orthodontic/orthopedic treatment. The section of conventional soft splints that is sandwiched by opposing sets of teeth is imprecise because it "gives" an irregular amount when the patient bites down under normal pressure, resulting in reduced TMJ stability in all dimensions.
Certain proposals have been made to make splints and other dental appliances out of two materials with differentiated hardnesses. Apparently, the idea is to use harder material in such appliances where harder material is needed and softer material where it is needed. For example, such proposals have been made in U.S. Pat. No. 4,448,735 to Huge, U.S. Pat. No. 3,404,056 to Baldwin, U.S. Pat. No. 2,934,823 to Preis and U.S. Pat. No. 2,789,351 to Gordon. However, none of the prior art proposals has been effective in overcoming the above-identified problems for splints.
Accordingly, it is a principal object of the present invention to provide an improved composition for a soft, persistently resilient, interocclusal dental appliance.
Another object is to provide such a composition that can be used for a dental appliance to impart in it the characteristic of being relatively soft and persistently resilient at mouth temperature for the working life of the appliance.
Yet another object is to provide an improved splint that adequately grasps the teeth of the user while also precisely retaining the mandible and/or TMJ in a desired position.
Another important object of the invention is to provide an improved splint that accommodates an immediate and accurate fit with the desired set of teeth jacketed by it and with the opposing set of teeth in contact with it.
Still another object is to provide an improved dental appliance that is comfortable to wear.
Yet another object is to provide a method of forming a plural-material interocclusal dental appliance from a unimaterial version of such appliance.
It is also an object of the invention to provide such an appliance that can be easily and cost-effectively manufactured.
In brief summary, one aspect of the invention includes a unitary plural-material, interocclusal dental appliance for use in connection with orthodontic/orthopedic treatment of the teeth and jaws of a patient's mouth. The appliance includes a first region made from a first material that provides a relatively hard, expanse with first and second surfaces, with the second surface being contactable by one such set of teeth. The second surface may be constructed with a substantially planar shape or with a shape that conforms generally to the cusps of such one set of teeth. A second region is joined to the first region, and is made from a second material that provides a relatively soft, persistently resilient enclosure for the other such set of teeth.
The second region includes plural zones, each of which is structured to allow an adjacent enclosed tooth to move toward the first surface of the first region, with such movement resulting in penetration of corresponding teeth into the relatively hard first material for a relatively precise distance. Such penetration defines lateral borders in the first material around such teeth so that the appliance accommodates relatively fixed lateral and vertical positioning of such enclosed teeth upon desired biting action by the patient.
Another aspect of the invention is a curable composition for making a soft, persistently resilient dental appliance. The composition includes a polymer component including either butyl or propyl methacrylate polymer, and a monomer component including either butyl or propyl methacrylate monomer. The soft, persistently resilient appliance formed from the composition of the present invention offers increased patient comfort and improved tooth retention.
Another aspect of the invention is a method of forming a unitary plural-material, interocclusal dental appliance for use in connection with orthodontic/orthopedic treatment of the teeth, jaws and mandible of a patient's mouth. The method is used in connection with conventional molding techniques usable to form a unimaterial interocclusal dental appliance in a corresponding cavity of a mold. The method of the invention includes the steps of (1) removing a first section of such conventionally formed unimaterial appliance to expose a surface of a second section of it, (2) putting such unimaterial appliance back in the mold so that a void is formed, the void being defined by the removed first section, (3) filling the void with curable material that is different from the material used to form such unimaterial appliance, and (4) curing the newly formed appliance so that the two materials bond together along the surface of the second section, thus to form a unitary plural-material, interocclusal dental appliance with the first section made from material that is different from the second section.
These and other objects and advantages of the invention will be more clearly understood from a consideration of the accompanying drawings and the following description of the preferred embodiment.